The catalytically essential persulphide groups at the molybdenum centres of xanthine oxidase and xanthine dehydrogenase are essential to interaction with arsenite (Edmonson et al., 1972; Cleere et al., 1974) Inhibition of xanthine hydroxylation may result from arsenite forming a complex with the persulphides and vicinal thiol groups (Massey & Edmonson, 1970). The NADH-dichlorophenol-indophenol ...

Various low-potential viologen dyes enhance light-induced absorption changes in the nearinfrared region (t.A870) in chromatophore preparations from Rhodospirillum rubrum in the presence of dichlorophenol indophenol and a high concentration of ascorbate (DCPIP + asc). An increase in t.A870 was also observed in large reaction-center preparations from R. rubrum with viologens in the presence of as...

The plastoquinone antagonist 2,5-dibromothymoquinone was found to inhibit NO-3 reduction from NADH by the nitrate reductase complex from wheat. It accepts electrons from NADH through the NADH dehydrogenase activity of the nitrate reductase. However, it does not inhibit the reduction of 2,6-dichlorophenol-indophenol by the enzyme. This suggests that the two compounds may be accepting electrons a...

We used a differential thermal detector in conjunction with an immobilized urease reactor to determine urea in serum. Samples (120 mul) are introduced into a flow stream and passed through an "adiabatic" column, which is packed with enough insolubilized urease to completely convert urea to ammonia and carbon dioxide. Measured temperature changes are directly proportional to the serum urea conce...

Conditions have been defined that enable the use of nitroprusside as a catalyst for the phenol-hypochiorite reaction when the latter is applied to measurement of nitrogen in Kjeldahl digests containing mercury. This is accomplished by lowering the concentration of mercury to a range where it remains effective in accelerating the destruction of organic matter during digestion but no longer react...

Conditions of oxidative stress may lead to cataract formation. Reaction of certain flavoproteins, the NADH: oxidoreductases, with different quinones is well known to form hydrogen-peroxide. This reaction was investigated to get more information on cataract induction by naphthalene and its quinone metabolites. Protein extracts from bovine lens cortex exhibit "diaphorase" activity, indicated as d...